Switch



SWITCH Filed Feb. 6, 1928 2 Sheets-Sheet l 9 1 v U w, W 5 |Il4| m m 5# We l w w z a WM U 0 W K 6i 2 a a @12 z 7 1 7 v y i I NV EN TOR.

A TTORNE Y.

J. D. BURKHQLDER SWITCH Filed Feb. 6. 1928 .2 sheetsus 2 ATTORNEY.

Patented Apr. 14, 1931 ,UNITED STATES PATENT oFF-icr.

JOHN D. BURKHOLDER, OF HARRISONBURG, VIRGINIA, ASSIGNOR T0 AUTOMATIC DE- VICES, ING, OF HABRISONBURG, VIRGINIA, A CORPORATION OF VIRGINIA swrrcn Application filed February 6, 1928. Serial No. 252,311.

This invention is directed to an improvement in electric switches designed for controlling the'flow of electric current for the generation of heat. 7

The switch is designed primarily for, though in nowise limited to, the control of the current for the generation of. heat in certain therapeutic devices, such for example as a blanket designed for general application to the body and a pad or pads'constructed for application to particular parts of the body. In this use, the switch is designed to provide a means whereby the degree of heat may be selectively controlled, the application of the current to the blanket or to the blanket and pad may beselectively controlled, and the switch may be automatically disconnected or opened following a predetermined degree of heat in either the blanket or pad.

The switch is constructed for selective manual setting and for manual or automatic disconnection or breaking to thereby provide for the control of the heating current at the will of the user, or automatically independently of the will of the user in the event a predetermined heat is reached in the therapeutic appliance.

The switch is designed to include an element providing an audible signal when the switch is closed and the current is flowing.

The invention is illustrated in the accom panying drawings, in which:

Figure 1 is a top plan view of the improved switch, the casing being in section and a plurality of therapeutic elements being shown in outline.

Figure 2 is a bottom plan of the switch.

Figure 3 is an edge view of the switch.

Figure t is a plan of the switch casing.

Figure 5 is a detail showing the contact strip controlling buttons.

Figure v6is a diagrammatic view showing a I modification of the automatic release for the ject-matter of the present application, comprises an insulating block or base 1 on the upper side of which are arranged two spring contact strips 2 and 3. These contact strips,

which are in the form of elongated strips of spring metal, are secured to one end of the base through the medium of downturned flanges 4- and 5 on the respective strips fixed to the base by screws 6. A conductor plate 7 is secured to the surface of the switch base and in electrical circuit through contact with the spring strip 3.

The connected terminal of strip 2 is, through the medium of the screws 6, electrically united to a plate 8 which overlies and rests upon the upper surface of the base, providing a conductor terminal 9. The contact strip 3 is similarly electrically united to conductor plate 7. A conductor strip 10 is secured to the upper surface of the base and extends longitudinally thereoi to a point adjacent the free ends of the contact strips 2 and 3, where the conductor strip is provided with a right angled portion 11 which underlies the free ends of the St1l)5 2 and 3 and is normally slightly spaced from the base.

The portion 11 of the conductor strip carries a contact point 12 underlying the contact strip 2 and contact point 13 underlying the contact strip 3, the relation of the parts being such that when the contact strip 3 is depressed, a contact on such strip will engage the contact 13 and depress the contact point 12 by moving the conductor strip 10 and right angled portion 11.

A conductor terminal 14 is secured to and in electrical connection with the conductor strip 10 adjacent its fixed end. A terminal connector strip 15 is secured on the base beneath the free ends of the contact strips 2 and 3, this terminal connector strip being preferably of right angled form with a por tion 16 underlying the contact strips 2 and 3 and a portion 17 extending longitudinally of the base and in electrical connection with a conductor terminal 18 to which the outgoing service wire is directly connected.

The portion 16 of the terminal connector strip is provided with contact points 19 and 20, the former underlying a contactpoint 21 on the under side of contact strip 2 and the latter underlying a contact-point 22 on contact strip 3. The contact strip 2 is provided with a further contact point 23 to cooperate with the contact point 12 on the portion 11 of the conductor strip 10, and the contact strip 3 hasa'n additional contact point 23 teengage contact point 13 on portion 11 of-con- V Iductor strip 10.

Thus, whenthe contact strip -2-is depressed, contact point 21 thereon will engage contact point 19 on the terminal connector strip, .15 and contact point 23 on such strip 2 will engage contact point 12 on conductor strip 10.

When contact strip 3 is depressed, point 22 thereon willengage contact point on the terminal connector strip 15 and at the-same I time contact 23 will engage 'the con tact 13 and each comprising upright portions 26 piv- "coe fiicients of expansion. The free end ofthe otally supported on the'ends of the base, as at 27, the upperends of the upright portions being'formed as hooks 28 beneath which the extreme ends of the-contact strips are'adapted to'engage whenthe strips are depressed,

the upright portions above thehooks being:

outwardly flared, as at 2 9, to insure the strips ridingbeneath the hooks in theoperation of the parts. The lower ends of the upright portions of the latches are extended beneath the base as tails'30, which tails diverge from the base andare normally held to maintain the hooks inoperative relation by'springs31 "arrangedbetween the tails and'bas-e. p

An automatic trip element 32is secured on v the under surfaceof'the"base,it being in'the form "of a thermostat involving a conventional construction, as of strips of different element has an upstandingflange 33 to which is secured a strip of non-conducting"mate rial 34 which directly underlies the tails of bothlatches 24 and25. Thestrip's making up the trip elementjare arranged to compel upward'movement of the free end of the ele- V .mentwhen'heated'to'a-predetermined degree, 55

so that the portion of the trip element thro ughapplication of the currentwill actu ate the latches to release'the contact strips 2 and 3 or either offthem position/ r i g mainc'ondu'ctor terminal35 is'secure-d to the underside of the base and a conductor 36 leads therefrom to'a coil 37 and from the latter to 'a conductor terminal 38; A spring when in operative strip 39 is-se'cu'red to the under side of the base, having its free end overlying the score of the coil 37 so that: in the passageof the current there is a slight vibration of the spring strip'and an audible signal incident to the contact of the strip with the core of the coil, thus providing the audible feature of the switch. 7 7

The trip element, or'morepart-icularly the plates making up such element, are heated through the medium of aconductor 40 coiled about the plates, such conductorhaving one terminal 4'lmfco'nnected to the terminal 14 on the conductor strip 10 and the other'terminal indicated at 41, leading to the therapeutic applianceor :other control device, as

will later appear. I r The use of the switch will be described in connection with the control of the heating of "therapeutic appliances, such as 'a'blanket and pad, though of course it is obvious-that the switch is adapted forthe'control of current for other uses. I r r The blanket is shown at 42 and the pad-at 43, The detailed structure ofthese parts is not important in the present application, except that the blanket contains an electric conductor 44 adaptedtoheat the blanket in the passage of currenttherethrough and the pad contains a conductor 45 for-the heating of the pad in the passage of the current. The

blanket and pad conductors are shown in series and connected by a conductor 46 leadingto the incoming main conductor terminal I 38 on the switch to which terminal the incoming service conductor 47 is connected'by te7rminal 35 and conductor 36 through coil The other terminal ofthe series conductor 44, '45 of the blanket and'pad is-connected by a conductor '48 to'the terminal 9 on the switch, that is, to the contact strip 2. A conductor 49 leads from conductor terminal plate 7 on theswitch to the blanket conductor 44 beyond the pad. As the conductor terminal 7- plate 7 is part of strip 3, it is apparentthat this strip 3 is therefore incircuit with the blanket to the exclusion of the pad.

At an appropriate point in the conductor 44-oftheblankeu'there is arranged atherm0 statinvolving bladesof strips ofdifferent co efficients-of expansion, one blade as 50 being in circuit with the conductor 44 and the other blade as 51 being in circuit with the conductor 41 leading to the con'ductorj4O coiled about the trip 32. A similar thermostat is arranged in -'the conductor 45*of'the pad, the

blades 52 and 53 of the latter thermo'stat, however, being connected to the conductor 45 at the entrance pointand exit point of the pad. V V 'Thesethermostats aresubstantially identi- 'cal in structure and will be referred to as reverse blade thermostats in that the blade H terminals are normally spaced and are brought lnto engagement in response "to a predetermined :degree 01? heat. The :"closing of the thermostatic blades serves to cut off the current, obviously in the case of the pad shunting the current entirely from the pad and in the case of the blanket operating the trip for the latches to release the contact strips 2 and 3.

The switch as an entirety is designed to be secured within a cylindrical casing made up of sections 54 and 55 having their mating ends adapted for threaded connection to provide for convenient separation when desired. The base 1 is secured in the section 54 by screws 56, and this section 54 is provided with two push-buttons 57 and 58 which extend through guides 59 in the casing and cooperate respectively with the free ends of contact strips 2 and 3; that is, the push-buttons overlie the free ends of the strips so that either strip may be operated into locking coopera tion with its latch by depression oi the par ticular button. The buttons are preferably constructed so that they may be rear ily distinguished by the sense of touch. for example, button 57 may have a pointed end while button 58 has a flat or rounded end.

A trip button 60 is connected to the trip element 32 and extends through the section 54 of the switch casing, permitting the trip to be operated manually at will. One end of the casing section 54 may be formed in any appropriate manner for the passage therethrough of the main conductors 47 and 61, the latter being the outgoing main conductor and being connected to the conductor terminal 18 on the connector strip 15 of the switch.

The remaining section 55 of the switch casing may be terminally formed for the passage therethrough of conductors 41, 46, 48 and 49. The switch as a Whole is thus arranged in the terminal cord which of course is adapted to be connected to any plug or light socket by an appropriate connector at the ends of the conductors 47 and 61.

Assuming the parts in the normal position indicated in the drawings and it being desired to heat the blanket and pad, push-button 57 on the switch is operated, depressing contact strip 2 and causing it to be held in depr ssed position by its latch 24. When this contact strip is depressed, contact points 21 and 23 thereon engage contact points 19 and 12 respectively. The current will now flow through the incoming conductor 47 to terminal 35, thence to the audible signal through conductor 36 and through a conductor 62 connected to the terminal 38 on the switch and serving as the incoming conductor to the pad and blanket in series. From the blanket, the current passes over a conductor 48 to terminal 9 on the switch through the contact strip 2, contact points 21 on strip 2 and 19 on connector strip 15 and thence through conductor 18 on the strip 15 and through the outgoing service conductor 61. This connection may be broken manually at will by operation of the trip button 60 and corresponding action of the trip element 32 to actuate the latch 24 to release the contact strip 2.

II", during the heating of the therapeutic appliance, the pad heats to a predetermined point, it will be cut out or shunted by the action of the thermostatic element including the blades 52 and 53. If the blanket heats to a predetermined point, the thermostatic element including the blades 50 and 51 is actuated by the heat and the currentdirected to conductor 41 to heat the trip element 32, passing beyond the coil of the trip element to terminal 14 on the conductor strip 10, through said strip 10 to contact point 12, thence through contact point 23 on strip 2 to and through contacts 21 and 19, thence through connector strip 15, terminal 18 and outgoing s rvice conductor 61. As the ther mostatic trip element 32 is heated by the current in the coil, it is automatically operated to exert pressure upon the tail 30 of latch 24 to release strip 2, breaking the continuity of current to the blanket.

It the blanket alone is to be heated, pushhutton 58 is operated, depressing contact strip 3. The current then flows through the blanket and back to the switch through conductor 49 to the plate 7, to conductor strip 3, through the contact points 22 and 20, connector strip 15, conductor terminal 18 and outgoing service conductor 61. T 16 auto matic release of this contact strip 3 occurs in the identical manner described in connection with the contact strip 2.

In Figures 6 and 8 there is illustrated a modified form of automatic release of the spring strips. In this modification, the spring strips, here indicated at 63 and capale of being operated by push-buttons 64 as in the preferred form, are designed to be engaged and held in contact or closed relation by a hook 65 pivotally supported at 66 and having a depending arm 67. hen in latching position, the hook bill overlies the end of the spring strip, the pivot 66 of the hook latch being on a plane above the strip when the latter is in locked position.

A trip element 68 a ranged below the base plate of the switch, this plate being substantially in L-form pivotally mounted at 69 near its upper end and formed with a lateral terminal 70 adapted to bear against the extreme lower end of the arm 67 of the hook latch. The trip member 68 extends past and serves as an armature for an electro-magnet 71, being projected below and beyond the magnet and provided with a spring 72 and bearing between the free end of the trip element 68 and the base.

In operative position, the bill of the hook overlies the spring strip 63, maintaining the latter in contact position, and the extreme end of the arm 67 of the hook latch rests in the spring strip 63 from moving the trip member.

When the electro-magnet 71 is energized, as by the closing of the thermostat 73 in the blanket, the trip member is attracted causing its lateral end 70 to move outwardly, that is, toward the right in Figure 6. In this movement, the free end of the lateral portion 70 of the trip member displaces the lower end of the arm 6? of the hook latch, finally freeing the latch and permitting the upward stress of the spring strip 63 to swing the hook latch on its pivot 66 to free said spring strip 63.

The parts are then in the positions indicated in Figure 8. Upon deenergization oi the electro-magnet, which of course follows the deenergization of the blanket by the release of the spring strip 63, the spring 72 tends'to return the contact member to normal position while the hook latch 67 will rest on top of 70. As either spring strip is moved to contact position, the bill of the hook is displaced and rides over 70 into position shown in Figure 6, being prevented, however, from moving to a position to release the spring strip by. engagement of the free end of the arm 67 with the lateral portion 70 of the trip member 68; A push-button 74 is. arranged beneath the'trip member 68 to provide for manual operation of the same in a manner similar to the result of the energization of the electro-magnet. Thus, the spring strips may be released manually if desired in order to control the flow of current to the blanket either manually or automatically as described in connection with the preferred form. v c

In Figure 7 I have illustrated a slightly modified form of current means for the operation of the release thermostat. In the preferred form, a portion of the conductor of the blanket is utilized to take care of the current amperage during the current cut-01f operation. In order to avoid this use of a portion of the conductor of the blanket, the blanket control thermostat indicated in Figure 7 at 7 5 and corresponding to the thermostat 50, 5 1 ofthe preferred form is arranged in an independent circuit having a resistance wire 76 of suificient length and capacity to take care of the currentshunted therethrough in the closing of the thermostat. Otherwise the operation of this automatic release is as in'the preferred formand the parts shown in Figure 7, being similar to sponsive to heat conditions of the appliance for energizing the thermostat.

2. In a switch for controlling the energiza-;

tion of a therapeutic appliance, a plurality of spring strips for selective energization of the appliance, locking members for holding the spring strips in contact position, athermostat to operate the locking members to release the spring strips,.means responsive to heat conditions of the appliance for energizing the thermostat, and a push-button for operating the'thermostat at will to release the locking means.

3. A switch 7 energization of a therapeutic appliance, comprisin independent spring contact strips for controlling the current in accordance with the selected energization, a locking lever pivotally mounted adjacent the free end of each strip and formed to engage and hold the strip in contactposition, manually operable means for moving theselected strip within" the influence of the locking lever, and a single thermostat responsive to heat conditions of the appliance to cooperate with both levers for releasing the set strips. 1

i. A switch for controlling the selective energization of a therapeutic appliance, comprising independent spring contact strips for controlling the current in accordance with the selected energization, a locking lever pivotally mounted adjacent the free end of each strip and formed to engage and hold the strip in contact position, manually operable means for moving the selected strip within the influence of the locking lever, a single thermostat responsive to heat conditions of theappliance to cooperate with both levers for releasing the set strips,and a push-button for operating the thermostat without regard to the heat conditions of the appliance.

5. A switch for controlling the selective energization-of therapeutic appliance, comprising independent spring contact strips for controlling the current in accordance with the selected energization, a locking. lever pivotally mounted adj acent'the free end of each strip and formed to engage and hold the strip in contact position, manually operable means for moving the selected strip within the influence of the locking lever, a single thermostat responsive to heatconditions of the appliance to cooperate with both levers for releasing the set strips, and an audible alarm included in the circuit.

6. A switch for controlling the selective energization of a therapeutic appliance, in-

cluding a spring strip adapted when in contact position to energize the appliance for a for controlling the selective particular heat condition, a second spring strip adapted when in contact position to hold the energization of the therapeutic appliance for another heat condition, a latch adapted to automatically engage and hold each spring strip in contact position, independent means whereby the respective spring strips may be moved to contact position, and a latch releasing thermostat responsive to particular heat conditions in the appliance for releasing the set latches to free the strips.

7. A switch for controlling the selective energization of a therapeutic appliance, including a spring strip adapted when in contact position to energize the appliance for a particular heat condition, a second spring strip adapted when in contact position to hold the energization of the therapeutic appliance for another heat condition, a latch adapted to automatically engage and hold each spring strip in contact position, independent means whereby the respective spring strips may be moved to contact position, a latch releasing thermostat responsive to particular heat conditions in the appliance for releasing the set latches to free the strips, and a push-button for manually operating the thermostat independent of heat conditions in the appliance.

In testimony whereof I afiix my signature.

JOHN D. BURKHOLDER. 

